To clean windows of multi-story buildings, it is necessary for workers to suspend themselves from the top of the building and move horizontally and vertically across the sides of the building. Accordingly, safety of the worker is a primary concern as is efficiency and quality of work done.
Some methods for window washing involve suspending the worker from some solid base on the roof. For example, the worker could simply tie off to a fixed object on the roof and rappel down the side of the building, washing windows within his reach on the way down the building. One obvious disadvantage of this method is that the worker has very limited horizontal movement. To cover an area of windows of substantial width, the worker has to return to the top of the building and move the rappeling line. However, the worker may encounter the problem of having limited fixed objects on which to tie off the line. To overcome this problem, some methods have utilized a support stand which the workers transport to the top of the building which they will move around on the building as needed. This support structure, however, must be weighted down to balance the weight of the worker suspended over the side of the building.
To overcome the disadvantages of the above methods, window washers have utilized devices which more easily move along the top of the building. Some devices roll along the roof of the building using counterweights to balance the suspended worker. A disadvantage of these devices is that such devices are difficult to roll, because they are weighted down. Also, the device may encounter loose gravel, drains, air conditioning units and other obstacles on the roof and a worker must provide clearance for the device around such obstacles. Another disadvantage of these devices is that the suspended worker must either come back to the top of the building and push the device over or a second worker is needed to push the device while the first worker is suspended.
In attempts to overcome these disadvantages, devices have been developed which have a means to move along the parapet or fire wall of the building instead of the roof top itself. Examples of such devices are Straw U.S. Pat. No. 3,059,721; Shaw U.S. Pat. No. 3,620,331; Dutcher U.S. Pat. No. 3,491,851; Camp U.S. Pat. No. 1,423,998; and Finley U.S. Pat. No. 5,065,838.
Straw teaches a ladder device which hangs over the wall and supports a worker thereon. The device will roll along the wall when pushed. This device has the obvious disadvantage of being very awkward to use, as the worker must physically climbup and down the ladder. In addition, use of this device is limited to relatively short buildings.
Shaw teaches a suspension device which can be physically moved along the parapet wall. The device is adjustable for fitting across walls of varying widths. However, its vertical legs are not adjustable in length. This means that the device is not adjustable to parapets of varying heights or to avoid obstacles on the inside or outside of the parapet wall, and further cannot be adjusted to compensate for the torque exerted on the device by the weight of the worker.
Camp teaches a scaffold carrier which can be adapted to fit across and move along a parapet wall. However, Camp nowhere suggests its use to suspend a window washer or the like and in fact does not show an easy means for safely suspending a worker from the device.
Finley teaches a movable support for suspending a worker. However, the device taught in Finley rolls along the building roof, as well as the parapet, which has disadvantages as discussed above. The device taught also utilizes a counterweight which further impedes its movement.